New Factory Made Rocket Heater, suggestions?

Hello again everyone! Its Sky again. Some of you may recall my father and I developed and are selling factory made Rocket Heaters tested to UL-1482 standards to meet building code and insurance policy compliant.

My father and I are developing a new model Rocket Heater. We have some great concepts, and not all we will share, which include but are not limited to pre-heating combustion air. However, we want to be more proactive and meeting your needs. We've learned so much along the way and will continue to do so. I finished reading the Rocket Mass Heaters Builders guide (highly recommended!) and have immersed myself as much as I can. Now we would like to consult the cumulative wisdom and experience from the members of this forum, get a feel for what you guys want to see in a factory made Rocket Heater. To everyones relief, we have decided to use a cast refractory rated up to 3300 F. for the burn tube and heat ris and have a concept to greatly increase the refractory's resistance to thermal shock, which involves reinforcing the refractory with carbon fiber. I do not believe the carbon will burn away because its incased in the refractory, but correct me if I may be wrong or if any of you have concerns! We will also use a method to have the cast refractory shelled and protected by thick steel tubing and to keep all the surface exceptionally rough, much rougher than even firebrick. However, we have some questions for all of you!

Which would you prefer, a square heat riser or a round one? Either shape is equally acceptable and easy to manufacture for us.

How thick would you like to see the refractory? Whats the minimum for strength? Remember the refractory will be surrounded by super-insulation. I just dont want the cast refractory to ever crack or fall apart. I just need to know how thick a refractory needs to be for structural strength.

Would you like to see a catalyst on top of the heat riser, or do you think the temperatures are too hot for a firecat? This will add 100 dollars to the cost of the heater.

How large of a feed tube would you like to see, 6, 7, or 8 inches? Or something in between?

We would like to go with a square body on the bell instead of a cylinder. This would give the gases more surface area and volume to release heat into the room and make manufacturing easier and smoother. Do any of you have concerns or objections to this?

First off, I'm glad you are doing well enough with your initial model to keep the business going. The more variety in available approaches, the better, and if someone can get a manufactured version when they would otherwise not be able or allowed to build their own, that just spreads the awareness of the technology.

I don't have a more informed opinion than anyone else on minimum refractory thickness, but I think a round riser would be more durable, and probably a bit more efficient. Also, it would obviously require less material for a given system size - not an unimportant point when making them commercially. I don't think you would actually need a really heavy outer shell for the riser, as that region after the combustion zone has historically been demonstrated to have conditions not conducive to corrosion.

A 6" size would likely be easier to make as a shippable unit, and small enough to more easily find installation locations. I might consider a 6" batch box, as that is supposed to have the heating power of an 8" J-tube, so could power a larger system while keeping the smaller combustion unit size. What are you thinking with regard to connecting your units to owner-supplied mass storage? I would think there could be a way for your manufactured and listed product to have thermal mass put next to or around the exhaust without voiding the listing... is this true? If the unit you test and sell is designed to shed enough heat in itself that your exhaust could safely go up the chimney even if someone foolishly insulated the duct run (!), any kind of thermal mass would not negatively impact the assembly's safety.

A catalytic combustor would be irrelevant to a properly functioning RMH, so I don't see any advantage to including that kind of thing. I would even consider a sales point like "total efficiency and pollution reduction without a catalytic unit to worry about".

There is a thread here about inexpensive ceramic fiber heat risers, and that might be a technology for you to look at; it would reduce shipping weight, not require as much protection from shipping damage/cracking, and contain the insulation in a slender package, which could probably be fitted inside a metal shell for shipping and moving safety.

Glenn Herbert wrote:First off, I'm glad you are doing well enough with your initial model to keep the business going. The more variety in available approaches, the better, and if someone can get a manufactured version when they would otherwise not be able or allowed to build their own, that just spreads the awareness of the technology.

I don't have a more informed opinion than anyone else on minimum refractory thickness, but I think a round riser would be more durable, and probably a bit more efficient. Also, it would obviously require less material for a given system size - not an unimportant point when making them commercially. I don't think you would actually need a really heavy outer shell for the riser, as that region after the combustion zone has historically been demonstrated to have conditions not conducive to corrosion.

A 6" size would likely be easier to make as a shippable unit, and small enough to more easily find installation locations. I might consider a 6" batch box, as that is supposed to have the heating power of an 8" J-tube, so could power a larger system while keeping the smaller combustion unit size. What are you thinking with regard to connecting your units to owner-supplied mass storage? I would think there could be a way for your manufactured and listed product to have thermal mass put next to or around the exhaust without voiding the listing... is this true? If the unit you test and sell is designed to shed enough heat in itself that your exhaust could safely go up the chimney even if someone foolishly insulated the duct run (!), any kind of thermal mass would not negatively impact the assembly's safety.

A catalytic combustor would be irrelevant to a properly functioning RMH, so I don't see any advantage to including that kind of thing. I would even consider a sales point like "total efficiency and pollution reduction without a catalytic unit to worry about".

There is a thread here about inexpensive ceramic fiber heat risers, and that might be a technology for you to look at; it would reduce shipping weight, not require as much protection from shipping damage/cracking, and contain the insulation in a slender package, which could probably be fitted inside a metal shell for shipping and moving safety.

I wonder what the insulation value of that ceramic fiber is and how thick it is.

It is 1" thick, and the riser sections the thread discusses are 6" ID and 24" long. This thickness of this material is generally considered sufficient by itself for heat riser insulation.

I think the thread gives enough information for you to contact the manufacturer for detailed specs.

Glenn Herbert wrote:It is 1" thick, and the riser sections the thread discusses are 6" ID and 24" long. This thickness of this material is generally considered sufficient by itself for heat riser insulation.

I'm more interested in the R-value of the insulation, specifically btu-in/hr-F-ft^2 as I have a source for high strength 3300 F. rated cast refractory's that have a thermal conductivity value of about 6 btu-in/hr-F-ft^2

The manufacturer can give you that information; their address is in the other thread.

Glenn Herbert wrote:It is 1" thick, and the riser sections the thread discusses are 6" ID and 24" long. This thickness of this material is generally considered sufficient by itself for heat riser insulation.

I think the thread gives enough information for you to contact the manufacturer for detailed specs.

I believe I read that the vacuum formed ceramic heat risers were 2" thick, so a 6" ID would be 8" OD.

jonathan kedzierski wrote:

Glenn Herbert wrote:It is 1" thick, and the riser sections the thread discusses are 6" ID and 24" long. This thickness of this material is generally considered sufficient by itself for heat riser insulation.

I think the thread gives enough information for you to contact the manufacturer for detailed specs.

I believe I read that the vacuum formed ceramic heat risers were 2" thick, so a 6" ID would be 8" OD.

If its 6" ID and 8" OD then its one inch thick.

Sky Huddleston wrote:

jonathan kedzierski wrote:

Glenn Herbert wrote:It is 1" thick, and the riser sections the thread discusses are 6" ID and 24" long. This thickness of this material is generally considered sufficient by itself for heat riser insulation.

I think the thread gives enough information for you to contact the manufacturer for detailed specs.

I believe I read that the vacuum formed ceramic heat risers were 2" thick, so a 6" ID would be 8" OD.

If its 6" ID and 8" OD then its one inch thick.

"open's mouth and inserts foot" 😃

How is this project coming along now?

John C Daley wrote:How is this project coming along now?

We're still trying to get the funds together to get it EPA Approved and Certified. We have been experimenting with refractory coatings and we're coming close to finding the right technology which will allow the heaters to without any doubt at all from anyone last indefinitely.